Re: [TCML] A Pearson autopsy

[Bert Hickman <bert.hickman@xxxxxxxxxx>]

Hi Finn,

Thanks for the photos and renderings - they, and the patent, were very 
revealing!

Since this particular CT has a 3db that extends from 125 Hz to 20 MHz, 
it's amazing that they are using a metallic strip wound core. Perhaps 
some type of Metglas or Permalloy? Pearson's original patent mentions 
using a ferrite core to maintain HF response.

The odd shaped termination wires and coupling to previous turns suggests 
they may be using capacitive compensation in addition to the distributed 
termination resistance.

Clearly, Pearson was one very clever guy - it looks like there may be a 
few more trade secrets still lurking within these devices beyond what 
the patent mentions... :^)

Bert

Finn Hammer wrote:
> All,
>
> A Pearson autopsy.
>
> The forensic lab has been working overtime to produce a report of the 
> late Pearson 2100 Current Monitor.
>
> Clad in copper, with it´s coat of green paint, it is a classy job, but 
> laying all stripped on the cooling board, what meets the eye looks like 
> something out of Kinrade´s estate:
>
> http://www.hammertone.com/temp/pearson/general.JPG
>
> Some of the potting removed reveals a high class strip wound core, 
> lamination not more than 2 thou thick, and wound with some fancy nickel 
> based metal.
>
> http://www.hammertone.com/temp/pearson/generalcloser.JPG
>
> There is nothing special about the main inductor winding, but the 
> terminating resistive winding is attached to it with some odd carrier 
> wires.
> I have tried hard to describe all this in words, but failed miserably, 
> so when the words count hit 1001 words, I fired up good old #DStudio, 
> and did a rendering of the whole wiring layout:
>
> http://www.hammertone.com/temp/pearson/3ds.jpg
>
> With this layout in mind, this detail photo gives more meaning:
>
> http://www.hammertone.com/temp/pearson/photo.JPG
>
> And even a poorly focussed closeup, where the termination wires can be 
> glimpsed:
>
> http://www.hammertone.com/temp/pearson/closeup.jpg
>
> I have been unable to get access to one of these wires, to measure their 
> thickness.
>
> Hope this helps some....
>
> Cheers, Finn Hammer
>
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